<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
      div{
        width: 0;
        height: 0;
        border: 5px solid transparent;
        border-top-color: green;


      }
    </style>
</head>
<body>
<div></div>

</body>
</html>